bugfix errormessage
add TODO
add function to calculate directivity index

Calculation is based on microphone position and weights, not on a
calculated beampattern. Therefore it should be more accurate and also
much faster.
deprecate beamSteering function
bugfix in coherenceMatNearfield
add tests
refactor variable name

To give correct description of what is used for calculation here. It is
the wave vector, not the steering vector.
check for NaNs in all cases
remove displaying of frequency on warning

Because this generated always warnings in octave.
add tests
remove beamSteeringNearfield function

Use <waveVec> or better <weightMatSynthesis_mvdr> instead.
This function was only giving correct results for far field, considering
that the output of the beamformer w^H*d should be equal to the number of
microphones. Using <weightMatSynthesis_mvdr> gives the correct result,
which is w^H*d=1.
add comments
take absolute and logarithm of result
incorporate new directivity index method into framework
vectorize beampattern calculation